1. Field of the Invention
The present invention relates to a semiconductor device, which can be simply manufactured and has a high frequency characteristic to be used in the range of, for example, 500 MHz to 1 GHz.
2. Description of the Related Art
A semiconductor device in which an integrated circuit such as IC, LSI is formed is contained in a packaged such as ceramics. FIG. 1 shows one example of a conventional semiconductor device. A semiconductor substrate 1 such as a silicon semiconductor having an integrated circuit is formed is adhered to a central part of a substrate mount section 2 formed of a ceramic substrate such as aluminum nitride.
For example, a lead 3, which is formed of a lead frame formed of an Fe alloy containing Ni 42 wt %, is adhered to a peripheral section of the substrate mount section 2 with insulating seal material 4 such as glass. Leads 3, 3 are formed at both ends of the semiconductor substrate 1 to have a distance, respectively.
By use of a bonding wire 5 such as an Au wire or an Al wire, an end (inner lead) of lead 3 is connected to a connection electrode formed on the semiconductor substrate to be electrically connected to the integrated circuit formed in the semiconductor substrate 1.
The substrate mount section 2 is adhered to a cap 6, which is formed of the same material as the seal material 4 used in the adhesion of the leads 3, 3. The cap 6 has a concave portion, and a main surface facing the substrate mount section 2 is formed to be concave. In the concave portion, there are provided the semiconductor substrate 1, the inner lead of the leads 3, 3 and the bonding wire 5 are formed to be sealed.
The cap material is formed of ceramic such as aluminum nitride, which is the same as the case of the substrate mount section.
The semiconductor substrate 1, which is mounted on the central part of the substrate mount section 2, is adhered to the substrate mount section 2 with a conductive adhesive 7 such as epoxy resin.
In recent years, the use of the semiconductor device under a high frequency condition has been increased. However, since a lead, which is formed of a lead frame, is used as a power source line in the above-mentioned conventional semiconductor device, inductance becomes large and noise is increased.
Since only the leads are used as a transmission line of the integrated circuit formed in the semi-conductor substrate, at least one of four leads must be grounded (GND) to prevent resonance when the leads are used in a frequency band of 300 MHz or more. Therefore, in this case, the number of leads must be 1.25 times the originally necessary number of leads.
Moreover, in a case of 500 MHz or more, transfer impedance must be matched in consideration of the transmission characteristic. Therefore, one of two leads must be grounded, and it is needed that the number of leads be doubled as compared with the necessary number of leads.
Furthermore, several signal lines are provided between the leads serving as GND, and distances between GND and signal lines differ, and are asymmetrical. Due to this, if the frequency exceeds 300 MHz, resonance is generated and impedance matching can not be obtained.